Solvent extraction of glycerides



260. CHEMISTRY, CARBON QWWH WU COMPOUNDS.

June 9, 1942. A. H. BATCHELDER 2,235,795

SOLVENT EXTRACTION OF GLYGERIDES Filed Aug. 2, 1939 2 Sheets-Sheet l IXER SEPARATOR SEPARATOR SEPARATOR SEPARATOR EXTRACT AUGUSTUS H. BATCHELDER INVENTOR (5 TORNEY Search 100 260. CHEMISTRY, CARBON COMPOUNDS. 423. 5

June 9, 1942. A. H. BATCHELDER SOLVENT EXTRACTION 0F GLYCERIDES 2 Sheets-Sheet 2 Filed Aug. 2, 1939 6 m m R v mmmmsmum 225,56 .1 e2 4 m w GLYCERIDES TO ACID RECOVERY TREATED TRAC 98 mum m :mum

zo B Exw Emiom F1 J AuousTus H. BATCHELDER INVENTOR T0 ACID RECOVERY ATTORNEY 260. ()HEMl'STRY, CARBON COMPOUNDS.

Patented June :1, 1:141

Search floor SOLVENT EXTRACTION OF GLYCERIDES Augustus H. Batchelder, Berkeley, Calif., assignor to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application August 2, 1939, Serial No. 287,977

Claims.

This invention relates to a process of treating mixtures of saturated and unsaturated compounds containing one or more carbonyl groups. More particularly, the invention involves a separation of mixtures of saturated and unsaturated glycerides such as occur in slow-drying or semidrying vegetable or animal oils to obtain a raffinate fraction and a quick-drying oil fraction.

A process for increasing the drying rate of vegetable and animal oils by separating certain fractions therefrom has been discovered. This process is of particular value in that it affords a means of obtaining valuable fast-drying fractions from cheaper or less valuable slow-drying, semidrying or even nondrying oils. Likewise the invention permits the recovery of highly stable, nondrying rafllnate fractions from less stable animal and vegetable oils.

A carbonyl group, such as an esterified carboxyl group present in animal and vegetable oils, is quite polar in nature. The polarity of compounds such as glycerides which contain the same number of ester groups is so nearly the same, by reason of the presence of these ester groups, that separation of mixtures of these types of compounds by selective solvents utilizing differences in polarity could not be predicted where the only significant difference comprises the presence of one or more unsaturated carbon-to-carbon bonds in the fatty acid constituent of the molecule. The fact that a given solvent is known to have a selective solvent action for unsaturated compounds where these compounds occur in mixtures with saturated compounds, and where there are no masking polar groups, has been found to constitute no valid basis for predicting the action of the selective solvent on glyceridesthls by reason of the presence of the masking carbonyl or ester group.

According to this invention, mixtures of saturated and unsaturated carbon compounds having masking carbonyl groups are extracted with a solvent having a selective solvent action for the unsaturated compounds in the presence of the carbonyl group to obtain an extract phase containing predominantly unsaturated carbon compounds and to obtain an undissolved raffinate phase comprising predominantly saturated carbon compounds. The two phases are separated by appropriate means and the unsaturated compounds separated from the selective solvent by distillation, precipitation or suitable chemical treatment.

Examples of mixtures of carbon compounds with which this invention is concerned comprise glyceryl esters of saturated higher fatty acids mixed with glyceryl esters of unsaturated higher fatty acids. These mixtures may be relatively simple ones, such as mixtures of glyceryl trioleate and glyceryl tristearate. However, the invention is particularly adapted for treatment of more complex mixtures such as occur naturally in slow-drying or semidrying animal and vegetable oils. Examples of this latter type of mixtures are: corn oil, cottonseed oil, rape oil, soya bean oil, walnut oil, and fish oils such as sardine oil. The process is also applicable to drying oils such as linseed oil to increase the drying rate thereof by separating a fast-drying fraction therefrom.

The invention in its broader aspects is not limited to the treatment of glycerides but includes mixtures of saturated and unsaturated esters of other polyhydroxy alcohols. Examples of other alcohols are:

Glycol;

Erythritol, CH2OH-CHOHCHOH-CH.2OH;

Arabitol,

CH2OHCHOHCHOHCHOHCH2OH; and

Mannitol,

CH2OH--CHOHCHOH CHOH-CHOH-CI-IzOH The invention also embraces in its broader aspects the separation of glycerides or other esters where polar groups other than the unsaturated bonds are masked by esterified carboxyl groups; for example, esters containing hydroxy substituted acids may be separated from esters containing unsubstituted acids. Such mixtures occur naturally in castor oils. The process of the invention is also applicable to other carbonyl-containing compounds but, as previously indicated, finds its greatest utility in the treatment of vegetable or animal oils.

According to this invention, a mixture of saturated and unsaturated carbonyl-containing carbon compounds is extracted with a solvent having a selective solvent action for the unsaturated compounds in the presence of the masking carbonyl group. The extract phase comprising the selective solvent with selectively dissolved unsaturated compounds is separated from the raffinate phase comprising undissolved components of the original mixture. The compounds in the extract are separated from the solvent in any suitable manner, as previously indicated. Solvent which may be present in the rafiinate can be removed therefrom when desired by distillation or other appropriate means. Examples of solvents having a selective action, as required in this I process, are: furfural, aniline, acetone, butyl alcohol, acetic acid, triethylene glycol, and methyl ethyl ketone. The temperature of extraction with the solvent varies with the oil being treated. the solvent being utilized, the proportion of solvent to oil, and the type of product desired. An appropriate temperature for any given set of conditions can be ascertained by a miscibility test. By way of example. when furfural is the selective solvent, temperatures below about 100 F. are suitable and from approximately 60 to 80 F. preferred. The proportion of solvent and the temperature of extraction preferably should be such that two phases exist-a solvent phase containing selectively dissolved compounds and an undissolved raflinate hase. However, the invention does not preclude complete solution of the mixtures in the solvent and precipitation of saturated compounds therefrom, as by cooling.

The extraction may be carried out by batch treatment, stage counterfiow, continuous counterflow, multistage counterfiow with solvents of different selectivity or multistage counterflow with the same solvent, the selectivity thereof being modified with or without separation of an intermediate rafllnate in one or more of the stages.

To illustrate modes of effecting the process of this invention a number of flow diagrams are shown in the drawings wherein Figure 1 illustrates a four-stage counterfiow process utilizing separate mixers and separators. Figure 2 illustrates a two-stage extraction process with an intermediate precipitation step and recovery of the selective solvent by distillation from the extracted oil. Figure 3 illustrates a system for preliminarily extracting free acids, then selectively dissolving certain glycerides, cooling the selective solvent to precipitate an extract fraction and, after separation of the precipitated compounds, cleaning up the selective solvent by a suitable scrubbing agent. Figure 4 illustrates a somewhat similar system except that selectively dissolved compounds are precipitated by a chemical treatment prior to separation from the selective solvent.

In Figure l, a mixture of saturated and unsaturated glycerides flows from storage tank 10, through valve-controlled line H, to mixer l2, where the glycerides are contacted with a selective solvent and passed to separator l3. The undissolved glycerides form a separate phase and when lighter than the selective solvent as here illustrated. flow from the top of separator l3,

through line 14, to mixer l5, where these compounds are again extracted with selective solvent and conducted to separator l6. Undissolved glycerides pass from the top of separator It by way of conduit 11, through mixer l8, separator l9, line 20, mixer 2|, separator 22 and conduit 23. to raflinate storage 24. Extraction and separation are effected in mixers l8 and 2| and separators l9 and 22, as in the previous stages. The selective solvent flows from solvent storage countercurrently to the glycerides by way of valve-controlled line 26, mixer 2|, separator 22, pipe 21, mixer 18, separator l9, conduit 28, mixer l5, separator 16, pipe 29, mixer 12, separator 13 and line to extract storage 3|. Both the extract and rafiinate may be suitably treated for the removal or separation of solvent and glycerides.

In Figure 2, the mixture of glycerides passes by way of valve-controlled inlet upwardly and countercurrently to a selective solvent through extraction tower 36. Undissolved glycerides continuethrough conduit 31, to extraction tower 38, where they are again extracted countercurrently by fresh solvent, and glycerides which are not dissolved in this second extraction stage form a separate phase and flow by way of line 39 to rafiinate storage 40.

Fresh selective solvent enters extraction tower 38 through inlet 41 to selectively dissolve compounds which were not removed in the first extraction stage, This solvent also cuts deeper into the mixture of glycerides and dissolves some of those compounds which more properly form a part of the railinate, that is, which are more stable to oxidation and/or polymerization than is desired in the final extract phase. The sol vent, together with its dissolved compounds, passes from the bottom of extraction tower 38, through pipe 42, to precipitator 43, where the above-mentioned dissolved rafilnate type compounds are selectively removed by precipitation which may be effected by any method desired. Suitable methods comprise cooling, or the addition of an antisolvent for th rafiinate compounds which is miscible with the selective solvent but immiscible with the rafiinate glycerides. or both cooling and addition of a modifying solvent. The solvent is separated from the precipitated compounds in precipitator 43 and flows through line 44 to extraction tower 36. The precipitated compounds are designated an intermediate rainnate and pass by way of conduit 45 to storage 46. The solvent, together with extracted compounds, is conducted from the bottom of extraction tower 36, through line 41, to still 48. where the solvent is vaporized from the extracted glycerides, condensed and cooled in condenser 49 and returned to extractor 38 by line 50. The extracted fast-drying glycerides are removed from the bottom of still 48 as indicated.

According to the process of Figure 3, glycerides such as animal or vegetable oils are subjected to a preliminary extraction treatment which selectively removes free acids without dissolving glyceryl esters in substantial quantities. This occurs in extraction tower where the mixture of glycerides is admitted through valve-controlled inlet 56 and a solvent having a selective solvent action for the acids is introduced through valvecontrolled inlet 51. The deacidified glycerides are passed to selective extraction tower 58 by means of conduit 59. A selective solvent having a selective solvent action for unsaturated hydrocarbons in the presence of masking carbonyl groups flows from storage 60 by way of valvecontrolled line 6| downwardly through tower 58, outlet 82 and cooler 63, to separator 64. Undissolved glycerides form a separate phase in tower 58 and are conducted by way of line to storage 66. In separator 64 extracted glycerides are precipitated and form a separate phase by reason of the reduction in temperature effected in cooler 63. The extract comprising these precipitated compounds flows through conduit 61 to extract storage 68. To avoid accumulated contaminations in the selective solvent it may be desirable to clean up the same after precipitation of the extracted compounds. This can be effected by passing the solvent from separator 64, through pipe 69, to scrubber 10, where the solvent is countercurrently contacted with a suitable scrubbing agent, The solvent is then returned by way of line 1|, to extraction zone 58. and the scrubbing agent, may pass from the bottom of contactor 10, through pipe 12 either to Q r H 260.CHENHSTRY,CARBON oCQlCh tor COMPOUNDS valve-controlled outlet 13 or where the scrubbing agent is suitable for selective removal of free acid from the raw glyceride mixture this agent may be conducted to acid extraction tower 55 by means of valve-controlled line 14. S01- as a tower packed with Raschig rings. Preferably the liquid levels in the extraction towers are controlled and maintained so that the selective solvent comprises the continuous phase and the glycerides are extracted by flowing as vents having a selective action for free fatty acids 6 discontinuous droplets through the tower. The are well known. Alcohol comprises a common undissolved portion of the droplets then coalesce example. The cleaning agent used in scrubber at one end of the tower as a separate phase and to clean up the selective solvent should be are removed. The solvent flows countercurrently immiscible with the solvent. Alcoholic water or to the droplets through the tower as continuous alcoholic caustic may be utilized with some 501- 10 phase and is removed from the opposite end vents. The process of Figure 4 is like that of thereof.

Figure 3 insofar as acid extractor 80, solvent ex- The following specific examples are given to traction tower 8| and scrubber 82 are concerned. illustrate results which may be obtained by uti- Inlet 83 for the acid solvent, 84 for the glycerides, lizing the process and principles of this invenand 85 for the scrubbing agent are like correlb lion. Oils were extracted using 4 volumes of sponding inlets of Figure 3. Undissolved glycfurfural at 75 F. to secure rafilnate and extract erides flow from 80 through line 86. extractor fractions. The effectiveness of the process in El and line 81, to raflinate storage 88. Selective separating the oil into saturated nondrying and solvent passes from storage 89 through valveunsaturated fast-drying fractions as indicated controlled line 98, extractor 8|, outlet 9|, chemby iodine value is given in Table 1:

ical treater 92, line 93, separator 94, conduit 95, Table 1 to scrubber 82, and is thence returned by pipe 96 to extractor 8|. The scrubbing agent flows as in Figure 3 from scrubber 83, to acid extractor ,Q E' Ramnme 80 by way of line 9'! or to discharge I00 as del iodine sired. The chemically treated extracted glyc- Yield Yield mm? erides precipitated and separated at 94 pass to storag 98 by way of conduit 99. Fem",

The use of chemical treater 92 and separator 23:23:2 rr 94 comprises the distinctive feature of the proc- 80 j 7 V 40 m m ess illustrated by Figure 4. Instead of precipir tating the extracted glycerides by cooling, addition of an antisolvent or the like. the glycerides In a second series of treatments sardine oil may be chemically modified in chemical treater was extracted with furfural utilizing a solvent to 92 to render these compounds insoluble in the so ail ratio of 2.3 to 1 by volume and a temperaselective solvent or to enable easier separation ture of F. in a countercurrent extraction by distillation. Suitable chemical treatment may lower packed with Raschig rings. The tests on be selected by those skilled in the art. The the oil charged and the extract and raiiinate chemically treated glycerides are then allowed to produced were as follows: form a separate phase at 94 whereby the solvent 40 Table 2 and the treated glycerides pass through their re- 7 u m V W spective conduits as previously indicated.

By utilizing the combination of selective extraction of free fatty acids in a stage prior to m u t ig;- selective extraction of glycerides as disclosed in 5 g gi F V j 1 Figures 3 and 4, a better and more efilcient jis y 8.? .1 48 separation of the saturated and unsaturated a 2' glycerides may be obtained where glyceride oils Iodine number... mo 222 13a normally containing free fatty acids are being treated. to

Throughout Figures 1 to 4 the glycerides are The change properties of the 011 produced removed from the top of extraction or separatby the furful'al treatment is shown by Observing zones. This will occur where the solvent is mg the comparative drying rates of the Origiheavier than the oil as is often the case. Hown94] sardine the mffinate the extractv and ever. the invention is not limited to the use of in y lin e d l. e h cont inin 1% of a selective solvents heavier than the glyceride mixmanganese lead drier and spread in a thin film tures and where the solvent is lighter the exto dry at 77" F. The results observed are tabutract will be removed from the top of the seplated below:

Table 3 Sardine oil Atstart Wet. Wet.. \Vol.. Wet. After3hr. Sticky Wet. Sticky Sticky. Aitor5hr. Tacky. Tacky Dry. Almost dry. After7hr... Almostdry....... Tacky Dry Dry. Altcr2llir..... Slighttackiness... Almostdry llnrilrlry. Slightlylucky.

aral-ing or extracting zones and the raffinate from the bottom thereof. In Figures 2. 3 and 4 countercurrent extraction towers are shown. These towers may be of any suitable type such The differences between the rafllnate and extract, and the superiority of the extract to linseed oil in drying rate. were even more apparent in a similar experiment where 0.25% of manganese lead drier was used in each oil and the following results obtained:

compounds by contacting said mixture with a selective solvent of the class represented by the Another indication of changed properties resulting from furfural extraction is given by the effect of heating at 600 F. on the viscosity of the extract and of the original fish oil in com- The above data show that solvent extraction of sardine oil will produce a material having markedly different properties than the original oil and similar or superior to those of highly priced vegetable oils such as linseed oil. Thus relatively cheap nondrying or semidryihg animal and vegetable oils may be treated to recover a highly desirable fast-drying oil fraction.

It is to be understood that the invention is not limited to the details herein set forth but is of the full scope of the appended claims. The process is applicable to a variety of compounds; for example, the process may be utilized in the treatment of carbonyl-containing compounds other than esters such as aldehydes, ketones, fatty acids, salts of fatty acids, and the like.

I claim:

1. A process of separating a mixture of esters selected from the group consisting of vegetable and animal oils into a relatively slower drying raifinate fraction, as indicated by a lower iodine number, and a relatively faster drying extract fraction, as indicated by a higher iodine number, which comprises selectively extracting relatively higher iodine number esters from said mixture with an organic selective solvent having a selective solvent action for said last esters by contacting said solvent and said oil below the temperature of complete miscibility of the solvent and the oil and above the melting point of the remaining undissolved oil fraction whereby two liquid phases are formed, one comprising the selective solvent with the higher iodine number esters dissolved therein and the other comprising the lower iodine number liquid hase raffinate, and recovering the higher iodine number [aster drying esters from said selective solvent.

2. A process for treating a mixture containing relatively more saturated carbon compounds and relatively less saturated carbon compounds. each type of said compounds containing at least one carbonyl group, which comprises separating from the mixture the relatively less saturated group consisting of furfural, aniline, acetone. butyl alcohol, acetic acid, triethylene glycol and methyl ethyl lretone and having a selective solvent action for said less saturated compounds, the temperature of contact being that at which the mixture is separated into two liquid phases. one comprising the selective solvent with the less saturated compounds and the other comprising a liquid raflinate phase of more saturated compounds, separating the liquid extract phase and the liquid rafiinate phase, and recovering said selectively dissolved less saturated compounds from said solvent.

3. A process for treating a material comprising a mixture of glyceryl esters having different saturations and different drying rates as indicated by diiierent iodine numbers which comprises separating from the mixture a relatively more unsaturated ester of higher odine numher than the more saturated esters of the mixture by extracting said material with a selective solvent of the class represented by the group consisting of furfural, aniline, acetone, butyl alcohol, acetic acid, triethylene glycol and methyl ethyl ketone and having a selective solvent action for said less saturated glycerides. the temperature of extraction being above the melting point of said glyceryl esters and such that two phases exist, one comprising a liquid solvent phase containing at least a major proportion of the relatively more unsaturated esters and the other phase comprising undissolved more saturated esters, separating the liquid extract phase. and recovering a relatively faster drying oll fraction from said extract phase.

4. A process of treating a mixture of esters. only some of which contain an hydroxyl group in addition to the esterified carboxyl group, which comprises selectively extracting said bydroxyl-containing esters from said mixture with an organic selective solvent having a selective solvent action for said last esters by contacting said solvent and said mixture below the temperature of complete miscibility of the solvent and the mixture and above the melting point of the remaining undissolved esters whereby two liquid phases are formed, one comprising the selective solvent with hydroxyl-containing esters dissolved therein and the other comprising a liquid phase rafflnate, and recovering the hydroxyl-containing esters from said selective solvent.

5. A process as defined in claim 2 in which the selective solvent is furfural.

6. A process as defined in claim 2 in which the selective solvent is aniline.

7. A process as defined in claim 2 in which the selective solvent is a polyethylene glycol.

8. A process for treating a mixture of saturated and unsaturated carbon compounds, each type of said compounds containing at least one carzou. bflLIVlIO I H l, UAHIISUN COMPOUNDS.

bonyl group, which comprises contacting said mixture in more than one stage with a selective solvent having a selective solvent action for unsaturated carbon compounds in the presence of masking carbonyl groups, separating a liquid phase extract comprising said solvent and selectively dissolved carbon compounds in each of said stages and precipitating a liquid phase intermediate rafiinate from at least one of said extract phases.

9. A process for treating a mixture of saturated and unsaturated carbon compounds, each type of said compounds containing at least one carbonyl group, which comprises passing said mixture through an extraction zone, passing countercurrently through said zone a selective solvent having a selective solvent action for unsaturated carbon compounds in the presence of masking carbonyl groups and precipitating selectively dissolved carbon compounds from said solvent by introduction of an anti-solvent at a point intermediate the ends of said extraction zone.

10. A process as defined in claim 8 wherein said precipitation is efiected by cooling.

11. A process for treating carbonyl compounds which comprises separating a mixture of compounds selected from the group consisting of vegetable or animal oils containing saturated and unsaturated glyceryl esters and free fatty acids into a relatively slower drying oil frac tion and a relatively faster drying oil fraction by selectively extracting free acids from said oil, contacting said extracted mixture with a selective solvent having a selective solvent action for o unsaturated glyceryl esters, separating a relatively slower drying liquid phase rafilnate and a liquid phase extract comprising said solvent and selectively dissolved unsaturated glycerides and recovering a relatively faster drying oil fraction from said extract phase.

12. A process for treating carbonyl compounds which comprises separating a mixture of compounds selected from the group consisting of vegetable or animal oils containing saturated Search 1100 and unsaturated glyceryl esters and free fatty acids into a relatively slower drying oil fraction and a relatively faster drying oil fraction by selectively extracting free acids from said oil, contacting said extracted mixture with a selective solvent having a selective solvent action for unsaturated glyceryl esters, separating a relatively slower drying liquid phase raffinate and a liquid phase extract comprising said solvent and selectively dissolved unsaturated glycerides and precipitating a relatively faster drying liquid phase oil fraction from said extract phase.

13. A process as defined in claim 12 further characterized in that unprecipitated compounds are scrubbed from said selective solvent after said precipitating operation.

14. A process for treating a mixture of saturated and unsaturated carbon compounds, each type of said compounds containing at least one carbonyl group, which comprises contacting said mixture with a selective solvent having a selective solvent action for unsaturated carbon compounds in the presence of masking carbonyl groups, separating a liquid phase extract comprising said solvent and selectively dissolved unsaturated carbon compounds, chemically treating said extract phase to facilitate separation of dissolved compounds from said solvent.

15. A process for treating a mixture of saturated carbon compounds and unsaturated carbon compounds, each type of said compounds containing at least one carbonyl group, which comprises passing a selective solvent having a selective solvent action for unsaturated carbon compounds as a continuous phase through an extraction zone in one direction, passing said mixture of carbon compounds as a discontinuous liquid phase through said zone in the opposite direction, coalescing and removing undissolved portions of said discontinuous liquid phase at one end of said zone and removing selective solvent together with the dissolved portion of said discontinuous phase from the opposite end of said zone.

AUGUSTUS H. BATCHELDER. 

